Understanding the mechanisms that regulate pancreatic beta-cell development is critical to the development of novel approaches to enhance regeneration and viability of beta-cells in patients with Type1 Diabetes. Our recent studies suggest key roles for two cell cycle genes, p57kip2 and cyclin D2, in differentiation and proliferation of pancreatic beta-cells during embryonic and postnatal life. Our goal in these collaborative R01 proposals is to explore further the roles of p57 kip2 and cyclin D2 in postnatal a-cell neogenesis and proliferation using novel "gain of function" approaches. Our Specific Aims are (1) To determine if postnatal a-cell neogenesis originates from the epithelial cells of the ducts and the role of p57kip2 expression in mediating post-natal beta-cell differentiation; these studies will use the combination of a novel model in which epithelial cells of the pancreatic ducts are derived from the transplanted bone marrow of GFP transgenic mice, and lentiviral vectors to express p57kip2; (2) To determine whether constitutive expression of cyclin D2 is sufficient to induce post natal beta-cell replication; these studies will use both in vitro (viral vector mediated gene expression in islet cultures) and in vivo (inducible expression of cyclin D2 in transgenic mice) models. These collaborative R01 applications bring together three investigators from the fields of developmental biology of the pancreas (Dr. Anil Bhushan), hematopoietic stem cell biology (Dr. Gay Crooks) and gene transfer and expression using viral vectors (Dr. Donald Kohn). The combination of expertise provided by this diverse group of investigators generates a unique opportunity for innovative and synergistic research relevant to Type 1 Diabetes.